Beyond the Solar System
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Transcript of Beyond the Solar System
Beyond the Solar System
Terms
• Quark– Subatomic particle– Makes up protons and neutrons
• Degenerate matter– Compressed atoms– Electrons pushed close to nucleus
Terms
• Interstellar– “Between the stars”– Any part of the universe not within a solar system
• Parsec (pc): 3.26 light-years
• Kiloparsec (Kpc): 1000 parsecs
• Megaparsec (Mpc): 1 million parsecs
Terms
• Magnitude– Brightness of a celestial object– Higher number = dimmer object
Beyond the Solar System
• Introduction to the Universe
• Interstellar Matter
• Classifying Stars
• Stellar Evolution
• Stellar Remnants
PSCI 131: Beyond the Solar System
Introduction to the Universe
PSCI 131: Beyond the Solar System
How the Universe is Organized
• Galactic clusters– Galaxies
• Stars/solar systems
• Where are we?
• Local Group galactic cluster– Milky Way galaxy
• Our solar system
PSCI 131: Beyond the Solar System – Intro to the Universe
Map of the Local Group. pc: parsec. Mpc: megaparsec.
Size of the Known Universe
• 100s of billions of galaxies
• Nearest large galaxy: 2.5 million ly (light-yrs)
• Furthest object observed: 13 billion ly
PSCI 131: Beyond the Solar System – Intro to the Universe
From: nasa.gov
Hubble Telescope “Deep Field” image. Most objects are distant galaxies.
History of the Universe• Age: about 13.7 billion years
PSCI 131: Beyond the Solar System – Intro to the Universe
From: tandempost.com
The Big Bang and the evolution of the universe. Matter has cooled and “clumped” over time to form galaxies and stars.
Interstellar Matter
PSCI 131: Beyond the Solar System
Interstellar Matter• Matter that occupies space between solar systems
• Mostly dispersed hydrogen and helium atoms (99%)
• Rest is atom-sized dust of other elements
• Nebula: localized concentration of gas and dust into a cloud
PSCI 131: Beyond the Solar System
Role of Nebulae• Birth of stars and solar systems
PSCI 131: Beyond the Solar System: Interstellar Matter
Types of Nebulae• Bright
– Emission– Reflection– Planetary
• Dark
PSCI 131: Beyond the Solar System: Interstellar Matter
Bright Nebulae: Emission• Emit their own
radiation
• Glowing gases
PSCI 131: Beyond the Solar System: Interstellar Matter
The Lagoon Nebula, 1,250 parsecs from Earth.
Bright Nebulae: Reflection
• Reflect radiation from other sources
PSCI 131: Beyond the Solar System: Interstellar Matter
The Merope Nebula, in the Pleiades star cluster.
From: thinkquest.org
Bright Nebulae: Planetary
• Envelope of gases ejected from a dying medium-mass star
• Gases glow (emit their own radiation)
PSCI 131: Beyond the Solar System: Interstellar Matter
The Helix Nebula, remnant of a dead Sun-like star.
From: thinkquest.org
Dark Nebulae
•Not hot enough to glow
•Not close enough to light sources to reflect
PSCI 131: Beyond the Solar System: Interstellar Matter
The Horsehead Nebula. From: nasa.gov
Classifying Stars
PSCI 131: Beyond the Solar System
Luminosity
•Brightness relative to the Sun (Sun=1)
•Expresses “true” brightness of an object– Distance from Earth is factored out
PSCI 131: Beyond the Solar System: Classifying Stars
The Herzsprung-Russell DiagramPSCI 131: Beyond the Solar System: Classifying Stars
Lum
inos
ity
Surface temperature
Brightest
Dimmest
Hottest Coolest
Stellar Evolution
PSCI 131: Beyond the Solar System
Two Key Forces Within Stars
• Gravity– Promotes contraction
• Gas pressure– Outward movement of gas and energy from star’s core– Promotes expansion
• Stellar evolution is a balance between them
PSCI 131: Beyond the Solar System: Stellar Evolution
Steps in a Star’s Life Cycle
• Birth• Protostar• Main-sequence• Red Giant*• Death
*Medium- and high-mass stars
only
PSCI 131: Beyond the Solar System: Stellar Evolution
Stellar evolution of a medium-mass star, plotted on the H-R diagram.
Stellar Birth• Contraction and heating of nebular gases (mostly hydrogen)
PSCI 131: Beyond the Solar System: Stellar Evolution
Protostar• Contracting nebula becomes hot enough to glow
PSCI 131: Beyond the Solar System: Stellar Evolution
Main Sequence• Nuclear fusion
begins
• Gas pressure balances gravity
• Star becomes stable
• Longest part of cycle
PSCI 131: Beyond the Solar System: Stellar Evolution
Red Giant
• Hydrogen fuel in core runs out
• Star expands, cools
PSCI 131: Beyond the Solar System: Stellar Evolution
Red Giant
• Core– Hydrogen fuel depleted, nuclear fusion stops
– Core collapses and heats up
– Heat radiates into outer shell
PSCI 131: Beyond the Solar System: Stellar Evolution
Red Giant
• Outer shell– Nuclear fusion continues
– Accelerated by heat from core
– More gas pressure, so outer shell expands and cools
PSCI 131: Beyond the Solar System: Stellar Evolution
Red Giant
• Outer shell– Gravity balances gas pressure– Expansion stops– Size of star becomes stable
• Core – Still contracting and heating: 2 million degrees F– Starts to fuse helium, forming carbon
PSCI 131: Beyond the Solar System: Stellar Evolution
Stellar Death: Low-mass stars
• Stars with less than one-half of Sun’s mass
• No red giant stage– Not enough heat from gravitational collapse
• Contract into a white dwarf star when hydrogen depleted
PSCI 131: Beyond the Solar System: Stellar Evolution
Stellar Death: Medium-mass stars
• Stars one-half to eight times Sun’s mass
• Core contracts into a white dwarf when helium gone
• Outer shell ejected into space: planetary nebula
PSCI 131: Beyond the Solar System: Stellar Evolution
Stellar Death: High-mass stars• Stars more than eight times Sun’s mass
• Core collapses– Heat causes outer shell to explode in a supernova
• Brightness increases by millions of times• Generates heavier elements (gold, lead, uranium, etc.)
– Collapsed core becomes a neutron star or black hole, depending on star’s mass
PSCI 131: Beyond the Solar System: Stellar Evolution
Stellar Remnants
PSCI 131: Beyond the Solar System
Types of Stellar Remnants
• White dwarf– Low- and medium-mass stars
• Neutron star– High-mass stars
• Black hole
PSCI 131: Beyond the Solar System
White Dwarf• About Earth-sized, but mass is similar to Sun’s
• Degenerate matter– Extremely dense
• A handful would weigh many tons
PSCI 131: Beyond the Solar System: Stellar Remnants
Neutron Star• Denser than white dwarf
• Electrons pushed into nucleus
• A handful would weigh millions of tons
PSCI 131: Beyond the Solar System: Stellar Remnants
Hypothesized cross-section of a neutron star. Note mass and diameter.
Black Holes• Densest known objects
• Remnants of highest-mass stars (more than 25 times Sun’s mass)
• Radiation (light) can’t escape gravity
PSCI 131: Beyond the Solar System: Stellar Remnants
Black HolesPSCI 131: Beyond the Solar System: Stellar Remnants
Artist’s conception of a black hole. Matter being pulled in gives off energy as it is compressed, creating detectable signals from around the black hole itself. Inset shows jet of electrons from a black hole in galaxy M87 (bright area).
End of Chapter